<div dir="ltr">Dear Becky,<div><br></div><div>I agree with Benedikt.</div><div><br></div><div><span style="font-family:arial,sans-serif;font-size:14px">> Also, is it ok to re-reference to a common average after having completed the following processing steps: 1) remove DC offset, 2) 0.1 high-pass filter, 3) epoch the data? </span></div>
<div><span style="font-family:arial,sans-serif;font-size:14px"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:14px">No problem.</span></div><div><span style="font-family:arial,sans-serif;font-size:14px">If your high-pass filter works correctly it should remove DC offset too. We recommend much higher freqs for it. Try 1Hz. It is to specify a pass-band edge, which is equivalent to 0.5Hz at -6dB.</span><br>
</div><div><span style="font-family:arial,sans-serif;font-size:14px"><br></span></div><div><span style="font-family:arial,sans-serif;font-size:14px">Makoto</span></div><div><br></div></div><div class="gmail_extra"><br><br>
<div class="gmail_quote">2013/9/29 Benedikt Ehinger <span dir="ltr"><<a href="mailto:behinger@uos.de" target="_blank">behinger@uos.de</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
Hi Becky,<br>
We exclude the bad channels before average reference, else you add a
small amount of the noise back into all channels. Keep in mind that
average referencing might reduce the rank of your data (compare the
discussions on the maillinglist for details).<br>
To your second question: I think all of these steps should not
interfere with the average referencing.<br>
<br>
Best,<br>
<br>
Benedikt<br>
<br>
<br>
<div>Am <a href="tel:26.09.2013%2014" value="+12609201314" target="_blank">26.09.2013 14</a>:28, schrieb Becky
Prince:<br>
</div><div><div class="h5">
<blockquote type="cite">
<div dir="ltr">Dear Makoto,
<div><br>
</div>
<div>
<div>Thanks for your response!</div>
<div><br>
</div>
<div>I'll be analyzing my data in channel space, so I'll go
with average referencing as you suggest. </div>
<div><br>
</div>
<div>Can you (or anyone else) please tell me whether to
exclude bad channels (including both mastoids and any
others) before or after applying a common average reference
to the data?</div>
<div><br>
</div>
<div>Also, is it ok to re-reference to a common average after
having completed the following processing steps: 1) remove
DC offset, 2) 0.1 high-pass filter, 3) epoch the data? </div>
<div><br>
</div>
<div>Many thanks!</div>
<div>Becky</div>
<div><br>
</div>
</div>
</div>
<div class="gmail_extra"><br clear="all">
<div><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">______________________________</span><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">______________</span><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
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<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Becky
Gilbert (nee Prince)</span><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">PhD
Researcher</span>
<div><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Room
A109</span>
<div><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Department
of Psychology</span><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">University
of York</span>
<div><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Heslington,
York, YO10 5DD, UK</span><br>
</div>
</div>
</div>
</div>
<br>
<br>
<div class="gmail_quote">On 25 September 2013 18:46, Makoto
Miyakoshi <span dir="ltr"><<a href="mailto:mmiyakoshi@ucsd.edu" target="_blank">mmiyakoshi@ucsd.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Dear Becky,
<div>
<div><br>
</div>
<div>> I believe the convention is to use the average
of linked ears or mastoids as the reference for
optimal measurement of these components,<br>
</div>
<div class="gmail_extra">
<br>
</div>
</div>
<div class="gmail_extra">It depends on whether you want to
use ICA to analyze your data in the source-resolved EEG
or not. If you do, re-reference does not affect the ICA
results. If you want to use channel EEG for the final
analysis, I recommend average referencing. If you need
to choose 1 electrode, choose Cz or FCz because that's
another 'convention' I've seen so far (may not specific
to your task though). Cz and FCz are easy to
interpolate.</div>
<div class="gmail_extra"><br>
</div>
<div class="gmail_extra">Makoto</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">2013/9/18 Becky Prince <span dir="ltr"><<a href="mailto:becky.prince@york.ac.uk" target="_blank">becky.prince@york.ac.uk</a>></span><br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
<div>
<div>
<div dir="ltr">Dear EEGLAB list,
<div>
<br>
</div>
<div>I've run an ERP study on auditory
temporal expectations in which I'm
interested in the auditory N2b and P3b
components. I believe the convention is to
use the average of linked ears or mastoids
as the reference for optimal measurement of
these components, but my mastoid channels
are consistently noisy in all of my
participants. The mastoid channels have
higher impedances (~15 KOhms) than the other
sites, probably due to the fact that the
caps we use have built in mastoid sites that
don't fit close enough to the skin. </div>
<div><br>
</div>
<div>I'm guessing it's a bad idea to
re-reference to noisy channels, so I'm
wondering what my options are. Can anyone
explain what they would do in this
situation? Are there any resources that
explain the effects of re-referencing on
specific components? I'm wondering if I'll
be able to see changes in N2b/P3b if I use
another reference, e.g. average of all
electrodes, and how the appearance of the
components (sites/polarities) will be
different from those typically reported with
a linked ear or mastoid reference.</div>
<div><br>
</div>
<div>Apologies for the fact that this isn't
strictly an EEGLAB question - I'm hoping
someone will still offer some advice!</div>
<div><br>
</div>
<div>Thanks,</div>
<div>Becky<br>
<div>
<div><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">______________________________</span><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">______________</span><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Becky
Gilbert (nee Prince)</span><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">PhD
Researcher</span>
<div><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Room
A109</span>
<div><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Department
of Psychology</span><br style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">
<span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">University
of York</span>
<div><span style="color:rgb(34,34,34);font-size:13px;font-family:arial,sans-serif">Heslington,
York, YO10 5DD, UK</span><br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
</div>
</div>
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</blockquote>
</div>
<span><font color="#888888"><br>
<br clear="all">
<div><br>
</div>
-- <br>
<div dir="ltr">Makoto Miyakoshi<br>
Swartz Center for Computational Neuroscience<br>
Institute for Neural Computation, University of
California San Diego<br>
</div>
</font></span></div>
</div>
</blockquote>
</div>
<br>
</div>
<br>
<fieldset></fieldset>
<br>
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-- <br><div dir="ltr">Makoto Miyakoshi<br>Swartz Center for Computational Neuroscience<br>Institute for Neural Computation, University of California San Diego<br></div>
</div>